In the field of dentistry, an important and delicate procedure is the cleaning of a diseased root canal to provide a cavity that is free of diseased tissue and antiseptically prepared for further sterile treatment, such as permanent embalming or filling with an inert or restorative material. This procedure is referred to as root canal therapy (RCT).
A root canal system includes the main root canal and many lateral canals that branch off the main canal, accessory canals, interconnections between the main canals, fins and dentinal tubes. Pulp and periapical diseases are, usually caused by bacteria invading and infecting the root canal system. An infected root canal system contains diseased or dead tissue and bacteria which results in inflammation and severe pain. Bacteria can exist in the root canal system itself or within other regions of the tooth structure such as the dentinal tubules, accessory canals apical deltas etc.
In order to eliminate bacteria from the root canal system a combination of mechanical instrumentation and irrigating solutions are used to remove or dissolve organic and/or inorganic debris, to destroy bacteria, to remove the smear layer and to maintain dentine permeability. As noted above, bacteria can exist in all parts of the tooth root many of which are inaccessible to mechanical and chemical endodontic procedures. Antimicrobial irrigants may reach some of the bacteria beyond the canals but they have limited effect as they are typically only used for a short period of time.
After instrumentation and irrigation, a dental material known as an intracanal medicament is placed into the canal until a later dental appointment when the root canal is filled with a permanent material. The rationale for dividing the treatment into different stages is to allow therapeutically active ingredients from the medicament to exert actions against persisting microorganisms in the root canal system. The intracanal medicament may also contain anti-inflammatory agents which are released into the environment of the root and which reduce the severity of inflammatory responses in the soft and hard tissues adjacent to the root. The primary purpose of intracanal medicaments is to eliminate microbes that have survived the chemomechanical preparation. Bacteria can remain because instrumentation has physical limitations, and irrigants have time limitations. Intracanal medicaments serve to supplement the antibacterial effects of chemomechanical procedures and they can predictably disinfect the root canal system, that is the walls of the root canal itself, the adjacent dentine with its tubular structures, the various accessory and lateral canals, voids and communications which are present, and the tissues immediately adjacent to the root from the crown region of the tooth to the end of the root.
Further purposes of such intracanal medicaments include, to render any remaining canal content inert, to dissolve tissue, to act as a barrier against leakage or breakdown of the temporary filing and to control seepage of apical fluids into the root canal system.
It is desirable that the intracanal medicament is long lasting, such that it is effective for days and possibly weeks after application. One such intracanal medicament (Ledermix) contains both an antibiotic (demeclocycline hydrochloride) and a corticosteroid (triamcinolone acetonide) as the active components and these are able to diffuse over a number of weeks in adult teeth.
Demeclocycline is a member of the tetracycline family of bacteriostatic antibiotics which exert actions on protein synthesis by binding to ribosomes. It has been demonstrated that tetracyclines form a strong reversible bond with hard tissues and that they exhibit slow release over extended periods of time. Antibiotics from this family have been found to exhibit antibacterial substantivity for several weeks.
However, one major problem with the presence of the tetracycline antibiotic demeclocycline in such medicaments is that upon exposure to sunlight teeth staining occurs. This is due to the formation of strongly coloured compounds between the dentine of the roots and crown of teeth and the demeclocycline, which then undergo photo-oxidation. This problem limits the application of medicaments containing demeclocycline in clinical dentistry. When tetracycline antibiotics are ingested during childhood and incorporated into forming tooth structure, a similar issue arises with their incorporation and the formation of further compounds, leading to tooth discolouration. The extent of staining which occurs when tetracyclines are ingested in childhood is known to vary according to the type of tetracycline chosen as well as the dose used and duration of exposure. While it appears that some tetracyclines when ingested in childhood may be less likely to stain teeth, there is no published literature available at the present time which indicates that alternative tetracycline agents could be used in medicament pastes to reduce or overcome the known issues with existing pastes based on demeclocycline.
AU2005220230 discloses a paste which contains clindamycin and triamcinolone as the active components, and claims that use of the paste does not cause staining of the tooth enamel. However, an issue with this choice of agents is the inherent or acquired resistance of major endodontic pathogenic enterococcal bacterial such as Enterococus facecalis. This bacterial species is very virulent and is generally found in root canal systems where treatment has failed i.e. the roots have developed an abscess, and the periapical area shows persisting inflammation after root canal treatment. Furthermore, clindamycin has little or no anti-inflammatory properties, and has no substantivity.
There has been a long felt need to provide long lasting medicaments which are more effective in eliminating bacteria from the root canal system, are effective in reducing inflammation, relieving pain and do not result in staining of the tooth structure.
Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date of each claim of this application.